This invention relates to moisture-stabilized foods, particularly to baked, ready-to-eat flour-containing products. Among the products which can be prepared in accordance with this invention are crumb-structured products such as cakes, dumplings, breads, bagels, refrigerated biscuits, quick breads, syrups, jams, jellies, condensed milk, and pet foods.
With regard to flour-containing products, all normally contain, in the final good, gelatinized starch. In addition, the technology of this invention can be used to prepare brownies and cookies which are of higher sugar and lower water content than the products previously described as crumb-structured, and are further characterized in that they are usually not as high in gelatinized starches.
One of the problems with such products is their very short shelf life. This is a distinct disadvantage for baked goods if one intends such products to compete with fresh bakery goods. To compete with fresh-baked goods, the products must maintain their fresh-baked characteristics, i.e., moistness, eating quality, tenderness, good taste and flavor.
Providing shelf-stable prebaked and packaged products is not an easy task. It is known that "staling" occurs within a short period of time for fresh-baked goods. Thus, those prepared at a bakery for immediate sale have a very short shelf life, typically a day or two, up to at most one week. Packaging can extend that shelf life somewhat, but again such products inevitably will stale in a short time, typically within a week or two, at most. "Staling" involves many different physical and chemical factors. Texture staling is caused by recrystallization of the gelatinized starches, moisture drying, chemical changes causing flavor changes, and microbiological spoilage. Of particular importance is recrystallization of the starches.
During baking, most of the starches of the type used in crumb-structured products become gelatinized; specifically, the starch swells and takes on water, the starch cell bursts, and the granular structure is lost. After a period of time, the starch begins to crystallize and assume a rigid structure. Some of the water in the starch migrates to the protein portion of the baked goods, making the product tougher and the crumb structure more rigid, and giving the consumer the impression of a dried-out product, even though the moisture content is the same. This starch molecule recrystallization or realignment is one of the main problems which destroys long shelf life for baked, packaged and shipped bakery products.
Many attempts have been made to improve the texture and shelf life of baked goods. For example, U.S. Pat. No. 3,950,545 describes the addition of a water-soluble polyhydric alcohol to stabilize baked products, preferably adding from 3 to 15% glycerine. In U.S. Pat. No. 4,503,080, doughs and cookies having varied textures and storage stability are described. Certain compounds known commercially as Polyol 6075 and olyol HM75 (trademarks of Lonza Inc.) are described as crystallization inhibitors. The latter compounds, misdescribed in that patent as "starch hydrolysates," are used to replace the sugar in the baked goods'formulations.
Similarly, U.S. Pat. No. 4,456,625 describes the use of polyhydric alcohols, again preferably glycerine, to extend shelf life. In this patent, the water content of the baked goods is carefully controlled.
Though the foregoing techniques were to some degree effective in stabilizing the products, the degree of storage stability was not as great as desired and in certain instances the balance of properties desired of the end product could not be achieved. In addition, the flavor of the product is often less than satisfactory.
With regard to the non-flour-containing products mentioned above (that is, syrups, jams, jellies, condensed foods, and pet foods), while the above-described mechanism does not apply, such products also tend to dry out, crystallize, and lose consistency and product integrity, thereby reducing their shelf life. In the case of condensed milk, the discoloration affects consumer acceptance and, in effect, shortens the shelf life of this product also.